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Abstract

Three experiments were conducted to evaluate the relationship of mesocotyl and coleoptile elongation to seedling vigor and plant height in rice (Oryza sativa). A laboratory experiment was conducted to evaluate the potential lengths of the mesocotyl and coleoptile of semidwarf and standard rice genotypes. Four genotypes exhibited inherent differences in their ability for mesocotyl and coleoptile elongation. The semidwarf genotypes ('M-101 ' and RU 7703008) showed reduced mesocotyls, coleoptiles, and total lengths (mesocotyl + coleoptile); whereas, the tall plant type ('L-201' and 'Labelle') had comparatively longer mesocotyls, coleoptiles, and total lengths. Itis assumed that mesocotyl elongation is the most important of the three parameters evaluated in seedling vigor, but total length is the least variable. Significant differences were detected among seeding depths and genotypes in the greenhouse experiment for emergence percentage, emergence index, coleoptile, and mesocotyl lengths. The field experiment verified that the low seedling vigor was due to the shorter mesocotyls and coleoptiles of the semidwarf genotypes in this test and was primarily responsible for poor stand establishment.